(1) Field of the Invention
The invention relates to tobacco drying processes and, more particularly, to a process for drying tobacco at controlled pressures above atmospheric to improve the smoking quality of tobacco and concomitantly increase tobacco fill value.
(2) Description of the Prior Art
It is generally well known in the art to dry tobacco destined for smoking articles such as cigarettes and the like at high temperatures, the tobacco having an initial moisture content usually above 16%. It also is well known in the food processing art to produce food stuffs by entraining a material such as food stuffs or pulp in a pressurized heated gas stream in suspended condition, thereby heating and conveying the material, and then discharging the material to a zone of lower pressure.
For example, U.S. Pat. No. 3,357,436, issued to A. H. Wright on Dec. 12, 1967 teaches improving tobacco fill valve by drying tobacco at a temperature range between 250.degree. F. to 600.degree. F. and controlling the moisture content of the tobacco to be dryed to between 16% and 35% to provide dryed tobacco of between 9% and 23% moisture content. U.S. Pat. Nos. 3,661,071 and its divisional No. 3,754,930, both issued to R. Toei et al, on May 9, 1972 and Aug. 28, 1973, respectively, teach the drying of food stuffs in a pressurized heated gas stream and discharging the same to a zone of lower pressure. Further, U.S. Pat. No. 3,734,104, issued to W. Buchanan et al on May 22, 1973, teaches rapidly heating and expanding moisturized tobacco for brief time periods of less than 3 seconds at temperatures as high as 750.degree. F. to increase tobacco fill value and U.S. Pat. No. 4,167,191, issued to J. Jewell et al, on Sept. 11, 1979, teaches drying expanded tobacco by heating tobacco in steam and air at temperatures of 250.degree. F. to 650.degree. F. in the presense of an absolute humidity at a level above that which produces a wet-bulb temperature of at least 150.degree. F. Moreover, two U.S. patents to B. Hedstrom, namely U.S. Pat. Nos. 3.808,093, issued on Apr. 30, 1974, and No. 4,043,049, issued on Aug. 23, 1977, as well as Canadian Pat. No. 879,811, issued on Aug. 31, 1971, teach drying of wood pulp in particulate form in entraining steam at elevated pressure, the steam heating and carrying the particulate pulp through the process. These aforenoted processes when involving tobacco have recognized the desirability of improving smoking quality and filling power but have either operated at atmospheric pressure when tobacco has been involved or, when operating under pressure, have involved food stuffs and wood pulps, requiring extensive and complex equipment in consideration of the nature of the product to be treated.
In accordance with the present invention an improved, straightforward, efficient and economical tobacco drying process is provided which recognizes the advantages and benefits of drying tobacco at both high temperatures and increased pressure but at the same time avoids the usually required extensive, complex and expensive equipment costs involved in high temperature and pressure operations. With the unique and novel process taught by the present invention, it is possible to obtain an improved tobacco product for smoking articles, such as cigarettes, which has smoother smoking qualities with lower impact and irritation properties and with lower nicotine or alkaloid type ingredients and, at the same time, increased fill values.
Various other features of the present invention will become obvious to one skilled in the art upon reading the novel disclosure set forth herein.